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Azoxybenzene from Nitrobenzene by Electro-
lysis.—Nitrobenzene can be conveniently converted intoazoxy-
benzene by electrolytic reduction. The apparatus required is
shown in Fig. 77.

It consists of a porous cell which forms the cathode chamber
and contains 20 grains nitrobenzene and 160 grams 2*5 per
cent, caustic soda solution. The two are kept well mixed
throughout the operation by a rapidly revolving stirrer. The
cathode is a cylinder of nickel gauze (12 cms. x 8*5 cms. = 100 sq.
cms.). The anode chamber is the outer glass vessel or beaker,

FIG. 77.
which contains a solution of sodium sulphate acidified with
sulphuric acid ; a cylinder of sheet lead serves as the anode.
An ordinary ammeter (A) and resistance (7?) are connected in
series with the battery and electrodes, and it is also useful,
though not essential, to insert a voltameter (F) between the
two electrodes. A current density of i to 5 amperes per 100 sq.
cms. is used and 15—20 ampere hours will complete the
The oily liquid which separates in the cathode chamber, and
1 The current may be obtained from a number of secondary batteries or from a
direct electric light circuit with a suitable resistance.                                  '•